It is considered a "special" evolution of Nincada, appearing only when Nincada evolves into Ninjask, starting at level 20, and there is an extra space in the player's party and the player has an extra Poké Ball. An extra Poké Ball is not necessary to obtain Shedinja in Generation III.

Biology

Physiology

Shedinja's body is based on a cicada's shed exoskeleton. Therefore, its body is completely hollow (it possesses no internal organs). The shell consists of chitin and is entirely incapable of movement. As it is the shed shell of a fully developed Ninjask, it has a similar shape to the latter. Shedinja's entire body is brown in color; the abdomen is of a darker shade. There are four protrusions where Ninjask's limbs were growing. What appears to be its eyes are actually slits; perhaps formerly for the Ninjask the shell housed to look through. Shedinja has one pair of what appear to be tattered "wings" on its back, which is actually where the exoskeleton was torn by Ninjask to break free of the shell. Between its "wings" there is a hole, out of which the Ninjask escaped. Each "wing" divides into three smaller pieces. These "wings" actually don't perform any function, as Shedinja's body is immobile and levitates. Two horizontal lines circle its abdomen. A white halo constantly floats above its head.

Gender differences

Shedinja is a genderless species.

Special abilities

It is rumored that if a human peers into its back, the human's soul will be stolen. This rumor was never mentioned in the anime.

Behavior

Shedinja appear to be wise and intelligent Pokémon. They are also very quiet and stealthy, like a ninja. They are protective over Ninjask but otherwise very little is known about them.

In the manga

In the Pokémon Adventures manga

Shedinja first appeared when Aqua Admin Amber, having been deprived of his Pokémon after being abandoned by Archie, borrows a Nincada from his comrade Shelly, which then immediately evolves into a Ninjask, putting Wattson in quite a pinch with the incredible speed it gained by the minute. Although the old Gym Leader eventually managed to defeat it, a Shedinja formed from the shell Ninjask shed and attacked him from behind, sending him sinking into the ocean.

Several more volumes down the line, both Emerald and Greta used Shedinja to exploit its Wonder Guard ability, as well as the fact that it has one base HP, requiring no items to resuscitate itself.

Shedinja's hard body doesn't move - not even a twitch. In fact, its body appears to be merely a hollow shell. It is believed that this Pokémon will steal the spirit of anyone peering into its hollow body from its back.

Trivia

From Generation IV onwards, a basic Poké Ball (a requirement for evolution) is removed from the bag upon evolution to produce a Shedinja. In Generation III, Shedinja instead copied the ball Nincada was in; this is the only legitimate way to get a Shedinja in a non-standard Poké Ball.

Shedinja inherits the same personality value, IVs, EVs, OT and ID number as the Nincada that shed it. Among other things, due to retaining personality value, if the Nincada was Shiny, Shedinja will be Shiny as well.

The Shedinja shed from a Nincada has no nickname, and the player is not given an opportunity to nickname it. The only way to give Shedinja a nickname is for the Nincada's original Trainer to take it to a Name Rater.

Shedinja's Ability renders it immune to 12 of 17 attack types, the most of any Pokémon. This also gives it a number of further distinctions:

Shedinja is the only Pokémon immune to Dragon Rage, which otherwise has the same effect against all types.

If Soak is used to make Shedinja a Water type, it will have immunities to 15 of 17 attack types.

Prior to Generation V, if Nincada learns a move upon evolving into Ninjask, Shedinja will also know this move. This means that Shedinja can learn any of Ninjask's level up moves starting at level 20, but only the ones learned at the same level. In Generation V, Shedinja starts with the moves Nincada knew prior to evolution.

Shedinja is the only genderless Pokémon that can learn Egg moves (as a Nincada). However, Staryu and Starmie could also learn moves via breeding in Gold and Silver.

Shedinja and Froslass are the only two Ghost types that evolve from a Pokémon that isn't a Ghost type.

Even though looking into the crack on Shedinja's back is said to steal one's spirit, all of Shedinja's back sprites display it perfectly, yet no negative effects happen to the player in-game.

1 HP trivia

Shedinja has many unique characteristics derived from the fact that it has only 1 HP:

Shedinja is the only Pokémon to have a stat not calculated by the standard formula; if it were, Shedinja would have at least 10 HP, even at level 1 with an HP IV of 0 and no HP EVs.

Shedinja's HP IV and base stat cannot be determined experimentally; one must find out the HP IV of the Nincada that shed it, as Shedinja shares those IVs.

Outside of battle, Shedinja immediately recovers from Poison after four steps in Generation IV onwards, whereas in Generation III it will immediately faint after four steps.

Despite it being able to learn Substitute and Rest, they will always fail; however, Shedinja can receive another Pokémon's substitute through Baton Pass.

Shedinja's Defense and Special Defense stats normally have no purpose in battle, as any damage will invariably cause Shedinja to faint. However, if Shedinja receives a substitute through Baton Pass, its Defense and Special Defense are factored into damage the substitute takes. Shedinja's Defense and Special Defense stats are also used when a Pokémon uses Transform on a Shedinja, and when Shedinja uses Power Trick (via Mimic).

Shedinja is the only Pokémon that has its HP restored to maximum when leveled up with a Rare Candy or revived with a Revive.

If Shedinja holds a Focus Sash and it is triggered, the item will be consumed and leave Shedinja at full HP. Similarly, if Shedinja uses Endure, it will receive no damage from the attack whatsoever.

In Generation V, if a Shedinja has Sturdy (for example, being hit by Worry Seed followed by Skill Swap with something with Sturdy) it can survive any direct attack. However, indirect damage, such as sandstorm, will bypass Sturdy and KO Shedinja.

If Shedinja were to use Endeavor, it would always reduce the opponent's HP to 1.

Origin

It is based on the shed husk that cicadas leave behind when they finish their metamorphosis into adults. It may also be based on a guardian angel, due to the halo-like object floating above its head. Its Ability Wonder Guard probably alludes to this.

Name origin

Shedinja is a combination of shed (to cast off skin or exoskeleton) and ninja.

Nukenin is a combination of 抜け殻 nukegara (casting off skin) and ninja. Nukenin is also a term describing ninja who have abandoned their clan and lord.